UPS602 Datasheet, PDF (7/12 Pages) Unisonic Technologies – HIGH PERFORMANCE CURRENT MODE POWER SWITCH

UPS602
LINEAR INTEGRATED CIRCUIT

FUNCTIONAL DESCRIPTION(Cont.)
(2) Switch Frequency Set
The maximum switch frequency decided by an external resistor R_T connected between pin R_T and ground. Then
the maximum switch frequency will depend on user requirement. The relation curve between f_SW and R_T as followed
FIG.5 under the condition of P_OUT/P_OUTmax=50%. The equation between f_SW and R_T as followed (1-2):
f_SW = -0.61*R_T+115.7--------------------------(1-2)
After R_T connected, switch frequency is also modulated by output power P_OUT during IC operating. So lower switch
frequency at lower load, which more and more improve IC’s efficiency at light load. Switch frequency is decreased
minimum at no load, then the UPS602 will operate at Power-Saving mode for Lower standby power. The relation
curve between f_SW and P_OUT/P_OUTmax as followed FIG.4 under the condition of R_T=75kΩ.
90
80
70
60
50
110V
40
30
220V
20
10
0 1% 2% 3% 4% 5% 6% 7% 8% 9% 10%
P_OUT/P_OUTmax
(RT=75KΩ)


FIG.4 The relation curve between f_SW and relative output power P_OUT/P_OUTmax





100
90
80
70
60
50
40
30
20
10
55 60 65 70 75 80 85 90 95
RT (kȤ)



( POUT/POUTmax =50%)


FIG.5 The relation curve between f_SW and R_T
UNISONIC TECHNOLOGIES CO., LTD
www.unisonic.com.tw
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QW-R119-005,A